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The other unanswered question with regard to this
increased incidence of spondylolysis and spondylolisthe-
sis is whether or not the inhibition of osteoclastic activity
by the treatment with bisphosphonates prevents remod-
eling of isthmic stress-related fractures. Ambulation also
clearly increases the risk of spondylolisthesis. In the
paper by Aström et al. seven of their 11 treated patients
developed spondylolysis once they became ambulatory,
whereas none of their control patients developed spon-
dylolysis or listhesis.
6
Many of the individuals evalu-
ated in our clinics have signs of repetitive fractures and
secondary elongation of the pars. It is unclear whether
or not these individuals truly have a dysplastic type of
elongation of the pars or repetitive fractures with incom-
plete healing and modeling of their fractures, which can
also be seen in their long bones.
have demonstrated significant progression of their slip,
either in the authors' experience or in the literature,
nor have any had significant pain to require aggressive
treatment. This population will need to be monitored
closely for progression of the spondylolisthesis (
Figure
44.17
). Conversely, the aggressive medical management
of these individuals, as well as improved surgical tech-
niques, may allow for more optimal fixation and fusion
than has been reported previously if they do require
surgical treatment in the future.
15,16,32,41,50,51
SUMMARY
Spinal fractures as well as spondylolysis and spon-
dylolisthesis are very common in individuals with all
types of OI. The goal of treatment of these individuals
is to prevent injury when possible, prevent progres-
sion of deformity when injury occurs and optimize
medical treatment early in life to allow for decreased
incidence and severity of fractures which will inevita-
bly occur, and when they do, to obtain better reconsti-
tution of vertebral height and vertebral morphology.
Paradoxically, the medical and surgical treatment of OI
has allowed individuals to become more active, which
predisposes them not only to acute and repetitive verte-
bral injury, but potentially to an increased incidence of
stress-related pars abnormalities. There is a great need
for ongoing study of these problems and little literature
to guide the treating physician. Treatment requires indi-
vidualized evaluation of the functional and structural
needs of the individual patient.
Orthotic management at this point has a very limited
role in the management of spinal fractures and spondy-
lolysis and listhesis. The majority of individuals seen
with anterior compression fractures as well as spondy-
lolysis and spondylolisthesis do not require active treat-
ment, but if progression to a high-grade listhesis occurs,
they may require posterior lateral fusion with or with-
out instrumentation depending on the severity of the
deformity in the bony architecture of the individual.
TREATMENT
There are isolated cases describing posterolateral
fusion for spondylolisthesis in individuals with OI.
However, none of these have been reported in the era of
bisphosphonate treatment. Many of these case reports
described marked elongation of the pars with severe
anterior translation of one or more vertebrae. Recent
reports on segmental spinal instrumentation in individ-
uals with scoliosis who are of adequate size and ade-
quate bone structure suggest that if an individual has a
symptomatic spondylolisthesis, acceptable fixation can
be obtained. However, there is no distinct literature to
ascertain what the ideal treatment is.
It is unclear whether the increased incidence of
spondylolysis and spondylolisthesis in these newly
ambulatory individuals with OI will lead to progres-
sion of the spondylolisthesis to the point where opera-
tive treatment may be necessary. In the study by Hatz
et al. none of the children had high-grade spondylolis-
thesis. However, it is of concern that this population of
mainly ambulatory children with OI was quite young
at the time of initial diagnosis. None of these children
